Alert Notice 410: Request for additional epsilon Aurigae observations

October 29, 2009

Dr. Robert Stencel (Denver U.) requests enhanced coverage of the bright,
long-period eclipsing binary star epsilon Aurigae through Wednesday.
Observations are requested beginning immediately (October 29, 2009; JD
2455134) and continuing through November 5, 2009 (JD 2455141).  This
request is in conjunction with scheduled observations with the CHARA
optical interferometer at Mount Wilson in California. Optical photometry
by a number of observers will provide a continuous photometric baseline
of epsilon Aurigae during the course of the interferometry, enabling
Stencel and collaborators to more easily interpret the interferometric

These interferometric observations are being made to image the system as
it enters eclipse; the optical interferometric observations being made
by CHARA are completely analogous to those made with radio
interferometers like the Very Large Array, and allow ground based
observers to obtain images with far higher resolution than a single
optical telescope is capable of.  The CHARA observations are scheduled
for the nights of November 1, 2, and 3 (through mid-day UT on November
4, 2009).  All observations, including visual estimates, DSLR and CCD
photometry, and photoelectric photometry, are encouraged.

The observations are part of a larger, long-term collaborative effort to
study epsilon Aurigae.  For more information on epsilon Aurigae, see the
Citizen Sky website:

Epsilon Aurigae is currently in the ingress phase of the eclipse, which
likely began in August of 2009.  The star is now near V ~ 3.4 and
declining.  The nature of the eclipsing object is not known, but is
likely to be an opaque disk surrounding an unseen, massive secondary
star or binary pair.  Interferometric images of epsilon Aurigae may
yield strong constraints on the shape of the eclipsing disk and size of
the system.

Epsilon Aurigae is located at the following (J2000) coordinates:

        RA: 05:01:58.134,   Dec: +43:49:23.91

Up-to-date charts of epsilon Aurigae may be generated via VSP:

A chart specifically for photoelectric and wide-field DSLR observers is
available at this URL:  [broken link]

For more background on the history of epsilon Aurigae see the January
2008 Variable Star of the Season article:

For more information on the Citizen Sky project please visit:

This AAVSO Alert Notice was prepared by M. Templeton.


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